Fluoropolymers are widely used in industrial applications because of their unique combination of chemical stability and high temperature properties. Certain applications, such as in the semi-conductor industry, demand the highest levels of stability and purity.
The process of polymerizing fluoropolymers results in end groups on the polymer chain ends which are determined by the type of polymerization initiator. Some of these end groups are reactive under certain conditions. Thus, they are a source of instability, albeit at a low level. Reduction of these end groups through fluorination is known and discussed in U.S. Pat. No. 4,743,658, EP 457 255, GB 1,210,794 and DE 1,901,872.
Extractable ions are contained in fluoropolymers as a result of current practices for the production of these materials. The level of these impurities may be increased as a result of the corrosion potential of the unstable end groups discussed above. When these unstable end groups come in contact with metal articles, such as process equipment or containers, impurities can result.
A need still exists for fluoropolymers with none of or very low levels of these impurities and for improved methods for their reduction and/or removal.